Three areas of study are covered in the final year of this grant. We are continuing investigations of the mechanism of reaction of anti-I-A antibody in reversing experimental allergic encephalomyelitis (EAE). T cell clones which induce EAE are central to this aspect of this study. These T cell clones are restricted to I-A molecules and recognize specific peptides on myelin basic protein. The second part of this investigation involves monoclonal antibodies directed against T cell subset markers. An antibody to the L3T4 antigen on helper/inducer T cells has been shown to reverse EAE as effectively as anti I-A antibody. The mechanism underlying this observation will be studied. Finally, we are using transposon induced mutations in Bordetella pertussis to design a safer pertussis vaccine. We have shown that transposon induced mutations which markedly reduce the amount of pertussis toxin available in these organisms leads to a greatly reduced encephalopathic potential.